Experimental furnaces are generally used to simulate combustion and deposition conditions in pulverised fuel boilers. The essential characteristics of such reactors are heating rate, high temperature, dynamic particle phase and atmosphere simulating conditions. For example, the essential components of an experimental furnace such as a vertical drop tube furnace system include a fuel feeder, a reactor and equipment for sampling and analysis. The drop tube furnace is a valuable tool when attempting to simulate coal combustion on a small scale. In this furnace pulverised coal is carried down through a water cooled feeder into a heated ceramic tube containing pre-heated air. After passing through the tube the particles are collected in a water cooled probe in different zones where the reactions are effectively quenched. The flow of these gases is kept sufficiently low to ensure that laminar flow conditions are met. Turbulent flow would cause the reduction of collection efficiency and the lowering of the sample integrity. The degree of decomposition experienced by the particles depends on conditions within the furnace. The residence time inside the furnace, oxygen content and the temperature can be altered as per the requirements.
Reference is made to U.S. Pat. No. 5,997,234, wherein a silicon pellet feed system has been described for use with a silicon melt furnace used to grow a silicon web. A reservoir for containing feed particles is coupled to the upper end of a feed tube. The lower end of the feed tube is positioned adjacent to a pair of rotatable drive rollers driven by a motor through a coupling and a pair of gears. The rollers are mounted at an angle with respect to horizontal and the outlet end of the roller feed path is located above a delivery tube leading to the silicon melt furnace. The elements are surrounded by an enclosure having a vacuum outlet for enabling the enclosure to be evacuated to a working vacuum level and a gas inlet for enabling an inert gas to be back filled into the enclosure. The feed rate is determined by the angle of the drive rollers, the speed of the motor and the shape of the bottom end of the feed tube. The rollers are resilient to provide enhanced surface friction for the particle flow and to prevent trapped feed particles from jamming the motor. The said system is not suitable for the purposes of an experimental furnace such as a vertical drop tube furnace system, which requires feeding pulverised coal to the furnace.
Prior art search for a feeding system for feeding pulverised coal to a furnace was made based on literature survey and patent databases, which did not yield any relevant references.
Therefore, there is a definite need to provide a feeding system for a furnace, specifically a system of feeding pulverised coal to a furnace, such as a drop tube furnace.